diff --git a/pkgs/servers/dns/knot-dns/default.nix b/pkgs/servers/dns/knot-dns/default.nix
index 394c76dbdb23..d052ddb7b79f 100644
--- a/pkgs/servers/dns/knot-dns/default.nix
+++ b/pkgs/servers/dns/knot-dns/default.nix
@@ -50,6 +50,7 @@ stdenv.mkDerivation rec {
   CFLAGS = [ "-O2" "-DNDEBUG" ];
 
   doCheck = true;
+  checkFlags = "V=1"; # verbose output in case some test fails
   doInstallCheck = true;
 
   postInstall = ''